Synthetically Tuned Pd-Based Intermetallic Compounds and their Structural Influence on the O2 Dissociation in Benzylamine Oxidation.

Intermetallic compounds (IMCs) have diverse electronic and geometrical properties to offer. However, the synthesis of intermetallic nanoparticles is not always easy; developing new methodologies that are conventional for many systems can be challenging, especially when incorporating highly electropositive metals to reduce to IMCs using solution synthesis methodologies. In this study, we report a comprehensive approach to access nanocrystalline PdxMy (M = Cu, Zn, Ga, Ge, Sn, Pb, Cd, In) intermetallic (IM) via the coreduction method employing sodium borohydride as the reductant. A combination of diffraction, spectroscopic, and microscopic techniques were performed to characterize the formed nanoparticles in terms of their phase composition, purity, particle size distribution, and surface oxidation properties of metals, respectively. IMCs of Pd with the elements such as Cu, Zn, Ga, and Ge exhibited higher catalytic activity that with elements such as In, Sn, Pb, and Cd. The DFT studies on these compounds revealed that the adsorption of benzylamine at the Pd site and the dissociative adsorption of O2 on the IM surface play a significant effect on catalytic activity. Among them, PdCu IM exhibited an excellent conversion of benzylamine (94.0%), with 92.2% of dibenzylimine selectivity compared to other IMCs. Moreover, PdCu exhibited decent recyclability and activity for the oxidation of different substituted primary amines.

Structure and chemical reactivity of the polar three-fold surfaces of GaPd: a density-functional study.

The polar threefold surfaces of the GaPd compound crystallizing in the B20 (FeSi-type) structure (space group P2(1)3) have been investigated using density-functional methods. Because of the lack of inversion symmetry the B20 structure exists in two enantiomorphic forms denoted as A and B. The threefold {111} surfaces have polar character. In both nonequivalent (111) and (111) directions several surface terminations differing in structure and chemical composition are possible. The formation of the threefold surfaces has been studied by simulated cleavage experiments and by calculations of the surface energies. Because of the polar character of the threefold surfaces calculations for stoichiometric slabs permit only the determination of the average energy of the surfaces exposed on both sides of the slab. Calculations for nonstoichiometric slabs performed in the grand canonical ensemble yield differences of the surface energies for the possible terminations as a function of the chemical potential in the reactive atmosphere above the surface and predict a transition between Ga- and Pd-terminated surfaces as a function of the chemical potential. The {100} surfaces are stoichiometric and uniquely defined. The calculated surface energies are identical to the average energies of the {100} surfaces of the pure metals. The {210} surfaces are also stoichiometric, with an energy very close to that of the {100} surfaces. Assuming that for the {111} surfaces the energies of different possible terminations are in a proportion equal to that of the concentration-weighted energies of the {111} surfaces of the pure metals, surface energies for all possible {111} terminations may be calculated. The preferable termination perpendicular to the A<111> direction consists of a bilayer with three Ga atoms in the upper and three Pd atoms in the lower part. The surface energy of this termination further decreases if the Pd triplet is covered by additional Ga atom. Perpendicular to the A<111> direction the lowest energy has been found for a bilayer with three Ga atoms per surface cell in the upper layer and one Ga and one Pd in the lower part. The calculated surface energies are in agreement with a simulated cleavage experiment. However, cleavage does not result in the formation of the lowest-energy surfaces, because all possible {111} cleavage planes expose a low-energy surface on one, and a high-energy surface on the other side. The prediction of Ga-terminated surfaces has been tested against the available experimental information. The calculated surface electronic density of states is in very good agreement with photo-emission spectroscopy. Calculated STM images of the most stable surfaces agree with all details of the available experimental images. The chemical reactivity of the most stable surfaces has been studied by the adsorption of CO molecules. The adsorption energies and maximum coverages calculated for the Ga-terminated surfaces permit a reasonable interpretation of the observed thermal desorption spectra, whereas for the Pd-terminated surfaces the calculated adsorption energies are far too high.

Ross and Ross-Konno procedure in children and adolescents: mid-term results.

OBJECTIVES: The aim of the study was to analyze mid-term results of aortic root replacement with pulmonary autograft in children and adolescents in two centers. METHODS: From December 1997 through August 2003, a total of 66 patients underwent the Ross procedure in two centers. Indication for Ross procedure was predominantly aortic stenosis in 24 patients and predominantly aortic regurgitation (AR) in 22 patients. Twenty patients with severe left ventricular outflow tract obstruction (LVOTO) underwent Ross-Konno procedure. No patient had a geometric mismatch of more than 5 mm in favor of the aortic annulus. RESULTS: There was no early death. One patient died 3 months after surgery due to bacterial endocarditis. Survival on median follow-up period of 2.4 years was 98.5%. Neo-aortic regurgitation was none in 29 (44%) patients, trivial in 35 (53%) patients and mild in 2 (3%) patients. One patient (1.5%) needed aortic valve replacement because of autograft failure. Actuarial freedom from more than trivial neo-aortic regurgitation, or aortic valve replacement was 95% at 5 years follow-up. There was no patient either with recurrent LVOTO or significant aortic root dilatation. Freedom from redo was 93% at 5 years of follow-up. There had been a significant reduction (P = 0.001) and normalization in the left ventricle diastolic diameter index and left ventricle mass index, respectively, within 3-12 months after operation. Sixty-three percent of all operated patients are without medication; no one is on anticoagulation therapy. CONCLUSIONS: Our 7 years experience with the Ross and Ross-Konno operation has shown excellent mid-term results, with mortality rate approaching zero in both simple and complex left heart lesions, even in the neonates and infants. It is a procedure of choice in children with severe anomaly of the aortic valve and/or left ventricular outflow tract obstruction. The main concern is dilatation of the neo-aortic root leading to progression of AR, especially in the settings of geometric mismatch of aortic and pulmonary roots and bicuspid, regurgitant aortic valve. The risk of autograft failure in these specific subsets of patients remains to be determined.

[Surgical treatment of total anomalous pulmonary venous return]. / Chirurgická liecba totálneho anomálneho pl'úcneho venózneho návratu.

BACKGROUND: Total abnormal pulmonary venous return (TAPVR), mainly the obstructive type represents the most riskful critical congenital heart defect requiring urgent surgery immediately after birth. THE AIM OF THE STUDY: Analysis of surgical correction of TAPVR results performed from December 1992 to December 1998. METHODS: Twenty-seven patients underwent surgery for TAPVR. 13 of them (48%) presented with hemodynamically severe obstruction. Mean age in the group with obstruction was 3.6 +/- 3.2 days with mean weight of 3282 +/- 537 grams. RESULTS: From the 27 studied patients 5 (18.5%) died. Mean duration of the study in the whole group is 1.91 +/- 2.01 years. Actuarial survival in the first month is 85%, in the second month 81% and remains identical in the 1., 2., 3., 4., 5., 6. year of the study. Univariate analysis identified operation before the year 1996 (p = 0.0056) as a risk factor of immediate mortality. Introduction of ultrafiltration significantly eliminated mortality (p = 0.0101). Remaining variables (age, weight, sex, obstructive TAPVR, TAPVR, extracorporeal circulation duration, pulmonary hypertension) did not significantly influence the survival (p more than 0.05). Multivariate analysis defined operation before the year 1996 as the sole risk factor of mortality (p = 0.0033). In patients operated on in the year 1996 (n = 15) was the survival in the studied period 100%. CONCLUSION: Since the year 1996 the results of surgical treatment of TAPVR significantly improved. The key role in the improvement have better urgent diagnostic and surgery, improvement of surgical technique and myocardial protection, introduction of modified ultrafiltration and the quality of postoperative care. Psychomotor development of children after correction is comparable with healthy population, all patients are in NYHA I class. (Tab. 2, Fig. 4, Ref. 9.)

Irradiation scheme using three daily fractions in the radiation therapy of pharyngeal and oral carcinomas.

A group of 34 patients were treated by irradiation using 3 daily fractions of 1 Gy each at 4 h intervals. The overall TD in all of the patients was 60 Gy administered within 26 days. The irradiation was carried out by telecurietherapy utilizing 60Co. Twenty-eight patients had the tumor in the oropharynx, 1 in the hypopharynx, 1 in the oro- and hypopharynx and 4 in the oral cavity. There was a prevalence of advanced clinical stages. At present 25 of the patients are living, 21 of them without clinical symptoms of the disease. The skin reacted to irradiation only with a slight erythema and hyperpigmentation. Irradiation reactions in the oropharyngeal and oral mucosa were grave and were accompanied by significant subjective complaints. No post-irradiation complications were observed.

Metastases into the cervical lymph nodes from unknown primary focus.

The analysis bears on 33 patients with histologically verified metastases into the cervical region from an unknown primary tumor, which was found intra vitam in 7 cases and by resection in 2 of the cases (i. e. 27.2%) only. The best form of treatment is a surgical-radiological combination. The search for the primary focus is often difficult and necessitates the use of ORL investigation and the other diagnostic methods. Emphasis is laid on the need of regular and frequent check-ups in case the primary focus is not detected. An early detection of the origin favourably affects the results of treatment.